Temperature indicator for motors



16, 1929. c, c, wHlTTAKER 1,709,643

TEMPERATURE INDICATOR FOR MOTORS Filed June 11, 19 .7

INVE-NTOR Char/es C W/zifia/Ier ATTORNEY Patented Apr. 1 5, 1929.

UNITED. STATES PATENT OFFICE.

CHARLES C. WI-II'ITAKER, 0F PITTSBURGH, PENNSYLVANIA, ASSIGNOR T0 WESTING- HOUSE ELECTRIC 6t MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VAE'IA.

TEMPERATURE INDICATOR FOR MOTORS.

Application filed June 11,

My invention relates to temperature-indicating devices and particularly to such devices in which the temperature indicated or measured is afunction of the change in resistance of an electrical conductor.

An object of my invention is to provide a temperatu1'eindicating device that shall be responsive to the. average temperature of all of the end turns of the coils comprising the stator winding of a dynamo-electric machine.

A further object of my invention is to provide a thermal element for a temperature-indicating device that shall be simple in construct-ion and easily manufactured, and;

A still further object of my invention is to provide a thermal element for an electroresponsive device that shall provide an efficient low-resistance path for the flow of heat from a body to the thermal element with which it may be in contact.

In practicing my invention, 1. provide a temperatureindicating device for such apparatus as dynamo-electric machines that comprises, in general, a l/ heatstone bridge that is provided with an electro-responsive indicating instrument which is responsive to an unbalance of the bridge.

The bridge consists of well-known resist ance elements connected in parallel circuit with each other, with the exception that. one of the resistance elements consists of a conductor having a plurality of return-bend convolutions.

The resistance element is placed within a sheath of absorbent material that may beimpregnated with a viscous substance for unit-. ingthe respective convolutions of the resistance elements and the sheath into a compact homogeneous structure The resist-anceelement so constructed is then placed around the end turns of the stator winding of the dynamo'electric machine and fastened in position by suitable securing means and a viscous ad-. hesive material, whereby an eflicient heat path is provided from the stator coils to the resistance element.

The resistance element, being so placed,

' may then be connected in the Vfheatstonebridge circuit, as previously statedherein.

For a fuller understanding of my invention, reference maybe had to the following specification, taken in COHjllIlCtlOilWVltll the accompanying drawing, in which v I Figure 1 is an expanded view illustrating a conductor having a plurality ofreturn-bent 1927. Serial No. 198,135.

convolutions and a device for determining the length of the convolutions;

Fig. 2 is an enlarged top plan view ofa thermal element embodying my invention;

Fig. 3 1s a View, in vertical section, of a dynamo-electric machine, to the stator of which is secured the thermal element illustrated in Fig. 2; and i Fig. 4t is a schematic illustration of circuits and apparatus embodying my invention.

In Fig. 1 of the drawings, a base 10is illustrated that is provided with spaced-apart pins 11 and 12, the distance between which is to be determined by the particular use to which itis put. A conductor-l3 is wound back and forth around the pins 11 and 12, whereby a conductor having a plurality of return-bent convolutions 14E is provided. In order that the respective convolutions shall be insulated from each other, the conductor 18 may either be enameled with insulating material or cotton covered. As shown, the convolutions or turns may be of such number that both ends of the conductor terminate at one end, i. e., at the pin 12, so that the conductor may be non-inductive, if so desired.

In order to hold the respective convolutlons '14 together tightly and compactly, a string 15 may be inserted through each of the loops at the ends of the various convolutions. The strings may then be drawnup as tightly as desired and tied in a convenient knot at. 16.

When the length of the conductor 13 has been properly determined, so that the resist. ance thereof is a fixed value at some base or reference temperature, the conductor 13 is insertedwithin an open-end sheath 17. In a specific embodiment of my invention, the, sheath 17 may be of such material as cotton cloth, woven in the form or shape of the or dinary flat shoe lace.

The assembly illustrated in Fig. 2 may be impregnated with such viscous adhesive materials or fluids as shellac or similar materials that possess electric insulating properties in addition to the properties which enable it to stick to a body with which it may be placed in contact. 7

A thermal element so constructed may be placed in position around the end turns 18 of a-stator winding of a dynamo-electric Inachine (see Fig. 3). The end turns 18 may be designated as the ends of the coils which constitute the stator winding, sides 19 and 21 of the coils being secured within the usual slots provided in a laminated magnetic iron structure 22.

When the sheath 17 containing the conductor 13 has been placed shown in Fig. 3, the strings 15 are tied together in order to secure the sheath in position. W ith the sheath in this position, it may be impregnated thoroughly with shellac in order that a good bond may be effected between the surtaceo't the ends of the coils and the surface ot the sheath. Vihen this is done, an efficient heat path is provided between the stator coils and the conductor 13.

When the thermal element illustrated in Fig. l to 3 has been lined in. position on the dynamo-electric machine, the ends of the conductor 13 may be connected in a lVheats'tone bridge circuit as shown in 4:. As there illustrated, the VVheatstone bri lge comprise' resistance elements 23, 24. and the conduc-- tor The bridge n'iay be energized from a source of E. M. F. 26 that 's connected to one end of the conductor 13 and to the common junction between the resistance elements L3 and 2%.

An indicating electro-responsive instrument 27 has one terminal thereof connected to the other end of the resistance element or conductor 13 and the other termina there to the common junction between the resist ance elements 2 and 25. It the tei'i'iperi'iture of the conductor 13 increases, the resistance thereot increases also, thus causing an unbalance in the Wheatstone bridge which pro duces a deflection in the instrument 2'? that is proportional to the change in temperature of the resistance element '13 from a fixed or ha. a temperature.

The resistance elements 23, 2% and may be of such material as manganin, which is a material that has a substantially zero temperature coei'iieient out resistance. The resistance element 13 may be of a material such as copper that has a relatively high temperature coeliicient of resistance.

It is preferred that the structure 13 be wound non-inductively, in order that any variations in current in the stator coils oi the dynamo-electric machine may not effect the indications of the instrument 27.

Since the end turns of the coils oi a dynam0electric machine protrude outwardly from the laminated magnetic iron structure 22, the means for dissipating the heat generated in the ends of the coils, caused by the PR loss incident to current flow therein, are not so efficient as in the portions of the coils which are in direct thermal relation with the magnetic structure The heat generated in the portions of the coils which are in direct con tact with the laminated iron structure 22 is conducted into the iron. Since the iron structure has a large thermal capacit", the

portion of the coils in contact therewith will not be heated to a very high tempera ture until the iron structure itself has been heated to a relatiyely high temperature. Since the ends of "he coils are not in direct thermal conductive relation with the iron structure and bethe cooling of the end turns is etl'ected y by air currents passing thereovcr, the ends are usually heated to a relatively high temperature.

TllGlGifOi'C, as the thermal element comp rising the conductor 13 and the sheath 1'? is wound around the end turns of the stator coils, an arc of the hot spots obtaining in the armatm coils is available to vary the resistance ot the conductor 13 substantially in are c with the temperature of the coi s. r .nc the change in resistance is a tunction ol' the tem er 'ure thercoit, any increase if temperatu re or the conductor 13 will arise an increasing deflection or indication to place in the instrument 27 whereby a ively accurate ten'iperature indication of ot a dynamo-elcctric machine I he olnained.

' invention, 1 have provided a thcr .nent for a lVhcatstone bridge circuit comprises a sl ructure having a plurality n-ben' convolutions that are disposed "i absorbent sheath, which sheath may -llliiQll with an insulating, heat (onv'scous fluid so that, when the eleola ed or attached to a body whose re is to be ascertained, an ellicient a may be effected from the heated thermal element. The thermal iple in construction, and easily id placed in position. oditications may be made in the device embodying my invention without delrom the scope and the spirit thereof. heretore, that only such limitations thereon as a imposed by the he appended claims. I as my invention: nbination, a stator winding, and a temperature-indicating device therefor, said device coii'iprising a source oi? electrmnotivc force, an electr0responsive indicating device and a Vi heatstone bridge, said bridge being electrically connected to said source of electromotive force and said indicating device, a portion of said bridge having a temperature coerlicient of resistance and being wound around the periphery of one en d of said stator winding and secured to said portion of the stator win ding by means of a binder, whereby an average of temperature indication of an entire end portion 01 the stator winding may be obtained.

2. in combination, a stator winding, and a temperature-indieating device therefor comprising a source of electromotive force, an electrores'-' onsive indicating device and a Wheats'tone bridge electrically connected to said source of electromotive force and said indicating device, a portion of said bridge having a temperature coefficient of resistance and being Wound non-inductively around the periphery of one end of said Winding in thermal relation therewith and secured thereto by means of a binder, whereby an average temperature of the entire end portion of the Winding may be obtained.

3. In combination, a coil structure and a temperature-indieating device for the coil structure, comprising a source of electromotive force, an electro-responsive indicating device and a Wheatstone bridge electrically connected at predetermined points to said source of electromotive force and said inclicating device, a' portion of said bridge having a temperature coefficient of resistance and being secured to a predetermined portion of said coil structure along the periphery thereof.

4. In combination, a coil Winding, and a temperature-indicating device therefor comprising a source of electromotive force, an electro-responsive indicating device and a Wheatstone bridge electrically connected to said source of electromotive force and said indicating device, a portion of said bridge having a temperature coefiicient of resistance and being non-inductively Wound and. secured to a portion of said coil Winding along the periphery thereof. v

5. In combination, a stator Winding, and a temperature-indicating device therefor,

said device comprising a source of electromo-' tive force, an electro-responsive device, and a Wheatstone bridge electrically connected at predetermined points to said electro-responsive device and said source of electromotive force, said bridge comprising a plurality of electrically-connected resistance arms, one of said arms comprising a return-bent loop conductor having a temperature coefficient of resistance, said loop conductor being secured to an end portion of said stator Winding along the periphery thereof.

6. In combination, a stator winding, and a temperature-indicating device therefor, said device comprising a source of electromotive force, an electro-responsive device, and a Wheatstone bridge electrically connected at predetermined points thereof to said electro-responsive device and said source or electromotive force, said bridge comprising a plurality of electrically-connected resistance arms, one of said arms comprising a return-bent loop conductor having a temperature coefficient of resistance and said loop conductor being secured to an end portion of said stator winding along the periphery thereof, and means for providing a thermally conductive heat path from said Winding to the loop conductor.

7 In combination, an electromagnetic Winding, and a temperature-indicating device therefor, said device comprising a source of electromotive force, an electro-responsive device, and a Wheatstone bridge electrically connected at predetermined points to said electro-responsive device and said source of electromotive force, said bridge comprising a plurality of electrically-connected resistance arms, one of said arms comprising a return-bent loop conductor having a temperature coefficient of resistance, said loop conductor being secured to an end portion of said electromagnetic Winding along the periphery thereof, said loop conductor being disposed along the periphery of one end of saidvvinding, and means for securing said loop conductor thereto and for providing a highly conductive path for the flow of heat from said Winding to the said loop conductor.

In testimony whereof, I have hereunto subscribed my name this 7th day'of June, 1927.

' CHARLES o. WHITTAKER. 

